Naphthenic acid derivatives and their preparation



3,%4,@2Z Patented Nov. 13, 1962 1 Claim. c1. 26t 429) This invention relates to naphthenic acid derivatives and to methods for preparation of such derivatives.

Petroleum naphthenic acids are complex mixtures of predominantly monocarboxylic, cycloaliphatic acids recoverable from petroleum by known procedures, generally involving formation of alkali metal soaps of the naphthenic acids and extraction of the soaps from the petroleum. Naphthenic acids have a wide range of molecular weights and boiling points, and the fractions recovered from petroleum generally are mixtures of components boiling through a range of at least 75 F., and commonly through a range of at least 150 F. The saponification number of a naphthenic acid fraction is an indication of its average molecular weight, the higher saponification number fractions having lower average molecular Weight and vice versa. The present invention contemplates preparation of derivatives of either relatively high molecular weight naphthenic acids having saponification number for example within the range from 120 mg. of KOH per gram to 200 mg. of KOH per gram, or relatively low molecular weight naphthenic acids having saponification number within the range from 200 mg. of KOH per gram to 320 mg. of KOH per gram.

It is known in the art to prepare esters of naphthenic acids with various hydroxyl-containing organic compounds, and such esters are useful to some extent in various applications. However the properties of the prior art naphthenic acid esters are not satisfactory in some uses, for example as primary plasticizers for polyvinyl chloride, and it would be desirable to prepare naphthenic acid derivatives which would have suitable properties for such uses. The present invention provides a novel manner of preparing naphthenic acid derivatives having a particularly wide range of usefulness in different applications.

The process according to the invention involves in one embodiment the contacting of naphthenic acid esters with ozone to produce compositions containing a greater average number of carboxyl groups per molecule than the charge material. It has been found that naphthenic acid derivatives having additional carboxyl groups in the molecule can be prepared, which have increased utility in various uses.

The contacting of naphthenic acid esters with ozone can be carried out under any suitable conditions. Satisfac ory results can be obtained at room temperature, but higher temperatures can be employed if desired. The higher temperatures generally result in the production of more highly oxygenated products than the lower temperatures. The production of more highly oxygenated products may be advantageous in providing more carboxyl groups'per molecule. On the other hand, it may be disadvantageous in producing excessive amounts in the molecule of other types of oxygen-containing functional groups, such as hydroxyl, aldehyde or keto groups, etc. Generally, it is preferred to employ oxidation temperatures not exceeding 150 F., but higher temperatures can be advantageously employed in some instances. Generally, it will not be desired to employ oxidation temperatures above about 300 F.

Any suitable ozone-containing material can be used as the contacting agent in the process according to the invention. Air and essentially pure oxygen are examples of particularly good gaseous mediums for the contacting agent. A generally preferred manner of preparing the ozone-containing gas is by passing air or oxygen through a Welsbach ozone generator or other suitable apparatus, thereby to produce a contacting agent containing for example 0.5 to 5 weight percent of ozone.

According to one embodiment of the invention, an ozone-containing material is contacted with esters of petroleum naphthenic acids. Such esters can be prepared from petroleum naphthenic acids and ester-forming organic hydroxyl compounds, according to procedures which are well known in the art. Suitable ester-forming organic hydroxyl compounds for such preparations include for example phenol, alkyl phenols, naphthol, alkyl naphthols, polyhydric phenols, the aliphatic alcohols, such as methanol, ethanol, n-propanol, isopropanol, butanols, hexanols, octanols, decanols, tetradecanols, hexadecanols, allyl alcohol, crotonyl alcohol, oleyl alcohol, etc.; aliphatic polyols, such as ethylene glycol, propanediols, butanediols, pentanediols, hexanediols, octanediols, octadecanediols, glycerol. erythritol, etc.; amino alcohols, such as aminoethanol, diethanolamine, triethanolamine, aminopropanols, aminobutanols, aminooctanols, etc.; aromatic alcohols, such as benzyl alcohol, phenyl propanol, phenyl hexanols, phenyl benzyl alcohol, etc.; alicyclic alcohols,

such as cyclohexanol, methyl cyclohexanol, amyl cyclohexanol, phenyl cyclohexanol, naphthenyl alcohol, etc.; heterocyclic alcohols such as furfuryl alcohol, tetrahydrofurfuryl alcohol, etc. Where polyhydric alcohols are employed, the alcohols may be either completely or partially esterified.

The contacting with ozone can be carried out under any suitable pressure, for example atmospheric pressure or elevated pressure up to about p.s.i.g. Higher pressures can be employed if desired, but it will usually be more suitable to employ relatively low pressures. The contacting should be continued until the saponification number has been increased by at least 5 mg. of KOH per gram, and preferably by at least 25 mg. of KOH per gram. Usually, it will not be desired to increase the saponification number by more than 200 mg. of KOH per gram, although greater saponification number increase can be obtained if desired. The time required to obtain the desired increase in saponification number varies according to the contacting conditions, and can be readily determined in the light of the present specification by a person skilled in the art. The rate of contacting of the naphthenic acid ester with the ozone-containing material is not a critical condition, and can be chosen in the light of the present specification by a person skilled in the art, in order to obtain the desired rate of reaction.

The product obtained in the contacting with ozone is a mixture of naphthenic acid esters containing additional carboxyl groups produced by partial oxidation, which groups are for the most part unesterified. These carboxyl groups can subsequently be esterified to produce a completely esterified material. The hydroxyl compound employed in the esterification can be the same used to prepare the charge ester, or it may be a different hydroxyl compound. The esters produced by such subsequent esterification have improved properties for use as plasticizers for vinylidene compounds and for synthetic rubber compositions produced by polymerization of butadiene compounds. Thus, for example, the resulting ester is generally compatible in larger concentrations with polyvinyl chloride than the original ester prior to the contacting with ozone.

In one embodiment, the invention provides vinyl polymers or other vinylidene polymers plasticized with esters obtained by esterifying additional carboxyl groups produced in contacting petroleum naphthenic acid materials,

i.e. naphthenic acids or salts thereof or naphthenic acid esters, with ozone. Vinylidene polymers include homopolymers, copolymers and inter-polymers of vinylidene monomers, examples of the latter being vinyl halides, styrene, vinyl naphthalene, acrylic acids, acrylic acid esters such as methyl acrylate and methyl methacrylate, vinylidene halides, acrylonitrile, vinyl acetate, vinyl benzoate, vinyl caproate, vinyl acrylate, vinyl ethyl ether, vinyl butyl ketone, etc. The esters prepared according to the invention can be used as vinylidene polymer plasticizers either alone or in combination with known plasticizers such as dioctyl phthalate, dibutyl phosphate, tricresyl phosphate, and the like. A particular advantage of the esters prepared according to the invention is that they are suitable for use as sole or primary plasticizers in polyvinyl chloride for example, whereas the naphthenic acid esters of the prior art have in general not been sufficiently compatible with polyvinyl chloride to be used as sole or primary plasticizers. The lack of sufficient compatibility has been particularly characteristic of the esters prepared from relatively high molecular weight naphthenic acids.

The proportion of esters to vinylidene polymer in compositions according to this embodiment of the invention is preferably within the approximate range from to 150 parts by weight of esters per 100 parts of polymer; more preferred proportions are those within the range from to parts by weight of esters per parts of polymer.

The plasticized polymer can be prepared in any suitable manner, e.g. by milling, molding, dissolving together in solvents, etc., such techniques being; well known in the synthetic resin art.

The esters prepared as described previously are also useful as plasticizers or extenders for natural or synthetic rubber compositions. Examples of suitable synthetic rubher compositions are those prepared by polymerization of butadiene either alone or with other polymerizable unsaturated monomers, e,g. styrene, acrylonitrile, methyl methacrylate, vinyl chloride, acrylic acid, etc. Polymerizable derivatives of butadiene, such as chloroprene, methyl butadienes, etc. can be employed instead of butadiene. The amount of esters employed in the plasticized composition is generally within the approximate range from 5 to parts per 100 parts of polymer. The larger amounts of esters, for example at least 30 parts per 100, within this range may be advantageously employed in the preparation of oil extended polymers, employing a polymer which has a raw Mooney viscosity (ML-4) within the approximate range from '80 to 240.

In other embodiments of the invention, the product obtained by contacting naphthenic acid esters with ozone can be hydrolyzed to produce free naphthenic acids, which can then be employed for various uses, such as the preparation of alkali metal salts of the acids, or heavy metal salts thereof. Heavy metal salts can also be prepared from products obtained by contacting naphthenic acids or salts thereof with ozone. The heavy metal salts have particularly satisfactory properties for use as drier soaps in paint and varnish compositions. Because of the increased average number of carboxyl groups in the molecule, it is possible to incorporate greater weight percents of the heavy metal in the drier soap composition, and the greater metal-contents increase the elfectiveness of the composition for catalyzing the oxidation of drying oils in the paint and varnish composition. The preparation of driers is Well known in the art, as disclosed for example by R. E. Kirk et al., Encyclopedia of Chemical Technology, vol. 5 (1950), at pages 195 to 204. The methods of preparation disclosed therein can be applied to the preparation of driers from the acids obtained by hydrolysis of oxidized V esters prepared according to the invention. Various heavy metals can be employed such as lead, cobalt, manganese, zinc, calcium, iron, copper, etc. The salts of heavy metals such as lead, strontium, etc., are also good stabilizing additives for vinyl polymers.

The following examples illustrate the invention:

Example I A mixture of butyl alcohol esters of naturally occurring petroleum naphthenic acids, prepared by esterifying a naphthenic acid fraction with n-butyl alcohol, was contacted with ozone to produce a composition containing additional carboxyl groups. The naphthenic acids employed to prepare the butyl naphthenate mixture conformed in preparation and properties to those sold com- "rercially under the trademark Sunaptic Acids B. Typical properties for such acids are the following: acid number 159 mg. of KOH per gram, distillation range 287-630 F. at 2 mm. Hg (098% The average molecular weight of the acids is about 330, and the average molecular formula is C21H3702.

The mixture of butyl naphthenates had a saponification number of 136 mg. of KOl-l per gram, and an acid number of 2 mg. of KOl-l per gram. The N.P.A. color of the mixture was 4.

Essentially pure oxygen was passed through a Welsbach ozone generator to produce an oxygen stream containing about 2 weight percent of ozone. This stream was introduced into a body of the butyl naphthenate mixture at room temperature at a rate of about 0.15 standard cubic feet per minute per thousand grams of butyl naphthenates. The introduction was performed at atmospheric pressure, and was continued for 9 hours. The product obtained had saponification number of 177 and acid number of 18, and N.P.A. color of 2. Further contacting with ozone under the same conditions for an additional 12 hours produced a material having saponification number of 220, acid number of 50, and N.P.A. color of 2.

The products obtained after 9 hours and 21 hours are compositions containing greater average numbers of carboxyl groups per molecule than the original butyl naphthenate mixture. These additional carboxyl groups can be esterified with n-butyl alcohol, or with a different alcohol, to produce compositions comprising esters of polycarboxylic acids. These esters can be employed as plasticizers for vinylidene polymers, rubber compositions, etc.

Example II The butyl naphthenate mixture described in Example I was contacted with ozone at a temperature of -210" F. for 35 hours, under conditions otherwise similar to those employed in Example I. The product was too dark to measure on the N.P.A. scale, and had saponification number of 323 and acid number of 118. This product was then esterified with n-butyl alcohol by refluxing with xylene in the presence of a small amount of p-toluene sulfonic acid as esterification catalyst. The resulting products were distilled to obtain afraction having saponification number of 228 and acid number of 12. This ester fraction has good properties for use as a vinylidene polymer plasticizer or rubber plasticizer.

Example III Example IV A plasticized polyvinyl chloride composition was prepared by milling together apolyvinyl chloride composition known by the trademark Geon 101and' the ester composition produced by esterifying with n-butyl alcohol the additional carboxyl groups in the 323 saponification number product produced in Example II by contacting n-butyl naphthenates with ozone. The esters, having saponification number of 201 and acid number of 2, were used in 40 weight percent concentration, based on total plasticized polymer. The esters were found to be fusible, by standard milling technique, with the polyvinyl chloride to produce homogeneous plasticized compositions having satisfactory flexibility, hardness, etc. Slight exuding of plasticizer occurred after two Weeks, but the plasticizer was very nearly completely compatible with Geon 101 in 40% concentration. Slightly smaller amounts of plasticizer can be used with complete compatibility, and complete compatibility at 40% concentration and higher can be obtained by preparing the plasticizer from products obtained by oxidation of the original esters to higher saponification numbers.

By way of comparison, the original n-butyl naphthenates, prior to contacting with ozone, do not produce a homogeneous composition in 40% concentration when attempted to be fused with Geon 101.- This shows that the esters according to the invention are more compatible with polyvinyl chloride than prior art naphthenic acid esters.

The naphthenic acid materials which are contacted with ozone according to the invention can be derived either from natural naphthenic acids, which can be recovered from petroleum without a separate oxidation step, or from naphthenic acids produced synthetically by the partial oxidation of naphthene hydrocarbons in the petroleum. Processes for liquid phase partial oxidation of petroleum fractions, such as wax or oil or mixtures of oil and Wax, in the presence of a metal naphthenate catalyst for example, are well konwn in the art. Although synthetically produced acids can be employed, such acids differ in structure and properties from natural naphthenic acids, and the latter are preferred starting materials according to the mvention. 5 This application is a division of application Serial No. 586,643, filed May 23, 1956, now US. Patent 2,911,433, which claims ester compositions as disclosed herein and process for preparing such compositions. In copeuding application Serial No. 769,101, filed October 23, 1958, now US. Patent 3,004,946, vinylidene polymers plasticized with ester compositions as disclosed herein are disclosed and claimed.

The invention claimed is:

As a composition of matter, metallic drier soaps of polycarboxylic acids, the metals of said drier soaps being selected from the group consisting of lead, cobalt, manganese, zinc, calcium, iron, copper and said acids having been produced by a process which comprises reacting petroleum naphthenic acid materials selected from the group consisting of naphthenic acids, salts of naphthenic acids and esters of naphthenic acids with ozone under conditions to provide increase in saponification number of at least 5 mg. of KOH per gram.

25 References Cited in the file of this patent UNITED STATES PATENTS Jezl Ian. 13, 1959 Jolly Nov. 3, '1959 

